Development of molecular markers for genetic and physical mapping of the PcDw locus in pear (Pyrus communis LL.)

Dwarf tree architecture is an important agronomic trait for modern fruit breeding and cultivation. The dwarf growth habit of pear (Pyrus communis L.), inherited from the pear cultivar 'Nain Vert', is controlled by a single dominant gene PcDw. To fine map the PcDw locus at higher resolution, 14 primer pairs for recently reported simple sequence repeat (SSR) markers mapped to the top region of linkage group 16 (LG16) in the apple and pear linkage maps, as well as 43 and 50 new primer pairs based on apple and European pear genome sequences for identifying SSR markers and single nucleotide polymorphism (SNP) markers, respectively, were analysed in the F1 progeny of an 'Aihuali' x 'Chili' cross by bulked segregant analysis. Eight new PcDw-linked markers, consisting of six SSR markers and two SNP markers detected by high resolution melting analysis, were obtained. Linkage analysis showed that the PcDw locus was flanked by the SSR markers CN993875 and QauSSR36, and that PcDw was mapped to scaffold00074: 137126- 163908 in the European pear genome. Six gene transcripts have been predicted in this region. Several closely linked markers were also tested in the F1 progeny of a '7- 34' x 'Zhongxiang' cross. In this case, the PcDw locus cosegregated with SSR markers CN993875 and QauSSR36. Our findings should facilitate the identification of PcDw in the pear genome and thereby help elucidate the molecular mechanism of the dwarf habit in pear.